


Lessons Learned

by orphan_account



Series: Like father, Like sons [3]
Category: Undertale (Video Game)
Genre: Discipline, Double Penetration, Ecto-Genitalia, I'll escort myself to the trashbin, Incest, M/M/M, Multi, NSFW, Spitroasting, Threesome, just pure sins, so many people requested this
Language: English
Status: Completed
Published: 2016-04-06
Updated: 2016-04-06
Packaged: 2018-05-31 17:48:36
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,503
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6480496
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/orphan_account
Summary: <blockquote class="userstuff">
              <p>After what happened while at work, Gaster feels he needs to punish his boys...</p>
            </blockquote>





	Lessons Learned

**Author's Note:**

> SO MANY people asked for this sequel, how could I not? I enjoyed writing this more than should have...
> 
> My writing requests are still open, btw. Just saying...

This had been the longest workday Gaster had ever experienced in his entire live.

And that was coming from the man who has to take part in the monthly overview meeting at the royal labs.

After his little... break, Gaster had thrown himself back into his research with renewed vigor.

He had actually gotten quiet a bit of work done after that. Maybe the unorthodox stress relief had been a benefit, though he would rather not mention that to his children.

His children, who had started this in the first place. Who needed to be taught a lesson.

Every time he shifted in his chair, a small wave of pleasure ran through him. It was residue magic that didn't dissipate as quickly as might have been practical. At least it didn't manifest into any unfortunate... appendages.

It just refused to let him forget what he had done. And what he had promised, as soon as he got home.

Monster biology could be so damn inconvenient at times. Gaster just hoped nobody noticed.

* * *

He closed the door behind him with a weary sigh, glad to be home. For various reasons, that was.

His sons where nowhere to be seen, and the royal scientist reveled in the momentary respite.

He loved his creations, he really did. But they could become quiet wearisome at times.

They were his entire world. His magnum opus, his greatest achievement, whatever you may want to call it.

And yet... sometimes they drove Gaster to absolute desperation... in the best and worst of ways.

"Ah, father. You're home." While he stood busy lost in thought, the very subjects of his reveries had entered the hallway. Papyrus smiled at him so sincerely, Gaster couldn't help but smile back.

Papyrus had that effect on many people.

"How was your day?" The young skeleton asked innocently. Gaster wasn't sure if he was acting or not. For all the demure air Papyrus seemed to radiate, their father knew from first hand experience how indecent his youngest son could really be if he set his mind to it.

"Quite well, despite some unexpected... interferences." He answered, keeping his face straight.

"Well, I hope you got your work done regardless." Papyrus started making his way to the kitchen as he spoke and Gaster followed in his wake.

Sans was at the table, nasal bone deep in some book or another. The cover declared it to be quantum physics, but Gaster knew better than to take that at face value.

"I was just finishing our diner." Papyrus announced proudly, face brightening in anticipation.

Gaster was fairly certain what it was. "Spaghetti!" What a surprise.

"How was your day, then?" Gaster asked them nonchalantly while eating.

"Uneventful." Sans immediately answered, with a completely straight face.

"We have not done anything out of the usual." Papyrus was a bad liar, face already tinging orange from that one sentence, but Gaster decided not to comment.

If this was how they were going to do it, two could play that game.

"I see." He counted the seconds, making sure the silence between his words stretched for the ideal amount of time. "That is peculiar to say the least."

He didn't continue right away and noticed both their eyes flicker to him, then to each other, in turn.  
He kept his mouth shut, pretending he didn't notice.

"What makes you say that, father?" Papyrus asked at last, not dealing well with the silence.

"Well... You two seem to be completely oblivious, but I am of the opinion you acted very troublesome today."

Papyrus began sputtering and blushing even harder. The poor boy was really not well-suited for these kinds of games, though he liked going along with them just fine.

Gaster had already deduced the entire thing had been Sans's idea.

His eldest son glanced at him from across the table with a slightly mischievous grin. "I am sure we don't know what you are talking about."

"I am sure you need some punishment."

"I am sure you wouldn't punish us if we don't know what we've done wrong." Sans sat back slightly as he said that. "That wouldn't be very fatherly of you."

"I see." Gaster pretended to consider this revelation. "In that case, I should be responsible for educating you properly."

* * *

"If I remember correctly, you were not wearing any clothes."

Even Sans's cheeks colored at the tone of voice Gaster was employing now. He like to call it his authoritative scientist voice, but Sans would just call it sexy.

They were in their father's room now, just like a few hours ago, when Sans had got the bright idea of starting this debacle.

Well, it was partly Papyrus's idea, if anyone cared to ask. Though that may seem hard to believe for some people.

Sans had been horny, Papyrus had been willing, and somehow some innocent kisses and snuggles had escalated into heavy petting and panting.

Which was when his younger brother had carelessly mentioned how nice it would be if their father was with them.

They had just wanted to include Gaster in the fun.

Somehow it lead to them now, standing at their father's bed, being asked to strip by that sinfully deep demanding voice, that really didn't take no for an answer.

Talk about escalation.

"Good." Gaster commented when his boys followed his command immediately. So eager to please, were they now?

He pulled up a chair from beside his desk, sitting himself down and allowing his eyes to hover over the two bare bodies before him.

So different and yet so similar, and both perfect in his humble opinion. Yes, he had done an excellent job on these two.

Sans tried to look defiant but his entire face was turning blue under the heavy scrutiny from his father, and Papyrus was even fidgeting nervously.

There wasn't much to see as far as naked skeletons were concerned, not when magic had not stirred to supply interesting... additions, yet.

But the way Gaster looked at them. Like he would happily devour both of them. The burning intensity of somebody utterly and completely pleased with the sight before him. It heated the entire room somehow.

"Well..." Gaster made a vague hand gesture toward the bed. "You were not standing around idly in the footage."

His boys observed each other silently for a second, both fully aware of what they had been doing back then.

Gaster was just starting to think they wouldn't do it, that maybe he had reasoned their motives wrong, when Sans turned and reached up, engaging his taller brother in a heated kiss.

Papyrus hesitated for the briefest of moments, but Sans was already allowing his hands to start roaming his brother's body, stroking the sensitive spine with gentle motions.

The two got utterly lost in the sensation quickly, allowing Gaster to just sit back and enjoy the show.

Magic was beginning to stir in the air, anticipation of what was ahead slowly raising.

Gaster's magic heated up faster than ever just watching his two boys enjoy each other so fully.

It was one of the most arousing things to see for him: his sons, his creations, HIS-

One souls in two bodies eagerly grasping at the chance to be whole again, even if it was for only a moment.

The poetic beauty might seem silly to some, but for the royal scientist who caused it, it was the most beautiful thing in the world.

The way blue and orange magic began to intermingle, blending effortlessly and filling the air with a dull glow. Gaster felt his own soul brighten in response, and it didn't take much effort at all for him now to summon a nice, thick member for himself to stroke.

Sans and Papyrus had gone from kissing and stroking to rutting incredibly fast, must have something to do with young monster's libido, their own magic genetalia brightening up the room as well.

Sans hissed as his brother rubbed the both of them in one hand, friction causing small sparks of pleasure to shoot through his body.

He remembered the text messages. The video. Knowing what was yet to come somehow made it better and worse at the same time.

The thought had barely crossed his mind or Papyrus was descending on him, wet heat engulfing his cock in one go.

Sans moaned and threw his head back at the sensation. His brother seemed quite eager at swallowing him whole, head bobbing up and down fast.

"A-h.. Ahn, Pap, I'm-" His cock was released with an obscene pop. Sans looked down into those bright eyes, his younger brother staring up at him questioningly.

Before he could say anything, Gaster was besides the bed, penis hanging out of the front of his unzipped pants obscenely.

Weren't he so busy trying not to cum before the script demanded it, Sans might have found the sight hilarious.

"Keep going." Gaster said, looking down at them with glee. Sans shivered beneath that gaze, but was reduced to moaning and grasping the sheets again as Papyrus returned to his previous occupation with zeal.

Gaster was gone again, and Sans had a second to wonder where the oldest skeleton had gone when he felt the sensation of his cock going impossibly even deeper down his younger brothers throat.

Papyrus gagged but didn't pull back, just kept going. Sans opened his eyes, mind clouded by an odd combination of intense pleasure and confusion.

It was then that he noticed his father again. He was still standing by the bed but... Oh god.

Gaster was sunken deep into Papyrus's rear, trusting a steady rhythm, grasping the young skeleton's pelvic bone to keep him still.

Every time their father moved forward, Papyrus chocked a bit more on Sans's cock, making the later cry out at the pleasure.

'That's what you get for lying to your father." Gaster addressed his youngest son, thrusting extra hard on each syllable for added emphasis.

Papyrus could barely grunt in response, eyes scrunched close as he was taken from both sides.

This position, while certainly pleasurable for his boys, would bring them no closer to a real climax, just as Gaster had intended.

Meanwhile, the sensation of tight heat wrapping around his cock in the most delicious manner brought him closer and closer to the edge.

Just a little more-

Gaster grunted in satisfaction as his orgasm ripped through him, thrusting in one last time while spurting his load.

Papyrus mewled a bit at the sudden feeling of being filled, but couldn't make much noise with his older brother's cock still deep down his throat.

Gaster pulled out with a sigh, appreciating his handy work.

"Very good, Papyrus. I think you have learned your lesson, haven't you." He laid his hand on the youngest skull with a contrite smile, loving the feel of heated bones beneath his palms.

Papyrus blushed even brighter orange, if at all possible, sitting back up and finally able to use his voice again. "Y-Yes, father."

"Good boy." Gaster felt the body underneath his hand shiver at the compliment. So responsive...

"Now for your brother."

The gaze Gaster sent his way could only be described as predatory, and Sans was filled with a renewed form of tension.

The kind that made his soul flare that much brighter and his magic flow faster because it knew he was fucked. In the good sense of the word.

"Get on your hands and knees."

Sans had never obeyed more rapidly in his life. He might have found this troublesome, was it not for the fact that he really rather get screwed right now. Literally.

Somehow his father was hard again, and in an instant, he was lining himself up and pushing in.

Sans could only gasp as the considerable girth breached him, bringing with it pain, but also so much pleasure. Especially as his father started moving, pulling out almost completely before pushing back in sharp and fast.

He grunted as Gaster picked up the pace, trusting at a steady pace, hissing at the slight burn as he was still sensitive from already having cum once.

Suddenly, Sans felt arms encircle his torso and pull him up, the cock inside him reaching even deeper than before.

He glanced through slitted eyes to see Papyrus still on the bed also, pleasuring himself eagerly.

There was something deliciously lewd about his younger brother stroking himself while watching Gaster fuck him.

Still not as lewd as Gaster's next question. "No need to do that yourself, Papyrus. Won't you join? Your brother still has room."

Gaster pulled at Sans's torso some more, so he was almost lying back in his father's lap, openly exposed to his brother. Papyrus hesitated.

"I- I don't kn-" He began, but Sans interrupted him by reaching his hand out and pulling his brother closer.

"Ngh- Y-yes... Pap, please. Yes-" He pleaded. The building pleasure running through him was already unbearable. He needed more.

Papyrus didn't need to be told twice. It took a bit of effort to find a position that would work, but then there was the feeling of something else sliding inside him, beside the thing already filling him to the brim.

Magic rushed to accommodate the new situation, easing the pain into a slight burn into a satisfying thrill into pure ecstasy.

He felt full. Fuller than ever before. Fuller than he thought possible.

But it felt good. Great, even. Fucking amazing, to be honest.

Sans nuzzled his head against his brothers collarbone, gasping and licking and biting just to occupy his mouth, to keep the constant stream of groans and whimpers from pouring out instead.

He was close, but there was no way in the world to articulate this. Instead Sans let it sweep him away, his cock trapped between his own body and that of his brother erupting, blue cum staining their chests.

Sans smothered the scream by bitting into his brothers neck, immediately feeling the taller body tense up at the sensation. A second later he was being filled by something warm and wet.

The world narrowed to this particular moment and nothing more...

It took him a minute to regain his senses. Sans was lying on the bed, half splayed on top of his equally debauched looking baby brother.

Gaster had pulled out also and stood besides the bed again. By the sheer feeling of it, he had not been far behind Papyrus, and Sans felt filled to the brim with brightly colored cum.

He loved it.

He was dimly aware of Gaster talking to him.

"I hope the two of you have learned your lesson about distracting me while at work?"

"Certainly." Sans managed, though his voice sounded slightly hoarse from the eager noises it had been making up until now. "It's a good way to get a great fuck."

Gaster simply rolled his eyes at him and left the room.

This might be a lesson that needed to be repeated a few times over to truly stick...

**Author's Note:**

> Find me on tumblr:
> 
> NSFW: https://www.tumblr.com/blog/skelejizz  
> SFW: https://www.tumblr.com/blog/sharada-n


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